U.S. patent application number 15/029941 was filed with the patent office on 2016-09-01 for method and apparatus for coding/decoding 3d video.
The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Jin HEO, Taesup KIM, Junghak NAM, Sehoon YEA.
Application Number | 20160255371 15/029941 |
Document ID | / |
Family ID | 52828401 |
Filed Date | 2016-09-01 |
United States Patent
Application |
20160255371 |
Kind Code |
A1 |
HEO; Jin ; et al. |
September 1, 2016 |
METHOD AND APPARATUS FOR CODING/DECODING 3D VIDEO
Abstract
The present invention provides a method for coding and decoding
a 3D video comprising a depth-map picture. The method for coding a
3D video, according to one embodiment of the present invention,
comprises the steps of: inducing a first index value with respect
to a first sample of a current block by mapping a depth lookup
table (DLT) on a predicted depth value of the first sample of the
current block which has been induced based on an intra-prediction
mode of the current block in a depth map picture; inducing a second
index value with respect to the first sample of the current block
by mapping the DLT on an original depth value of the first sample
of the current block; inducing a residual index value between the
first index value and the second index value with respect to the
first sample of the current block; and transforming, quantizing,
and entropy-coding the residual index value.
Inventors: |
HEO; Jin; (Seoul, KR)
; YEA; Sehoon; (Seoul, KR) ; KIM; Taesup;
(Seoul, KR) ; NAM; Junghak; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Family ID: |
52828401 |
Appl. No.: |
15/029941 |
Filed: |
October 20, 2014 |
PCT Filed: |
October 20, 2014 |
PCT NO: |
PCT/KR2014/009855 |
371 Date: |
April 15, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61892465 |
Oct 18, 2013 |
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Current U.S.
Class: |
375/240.13 |
Current CPC
Class: |
H04N 19/597 20141101;
H04N 19/187 20141101; H04N 19/11 20141101; H04N 19/159
20141101 |
International
Class: |
H04N 19/597 20060101
H04N019/597; H04N 19/11 20060101 H04N019/11 |
Claims
1. A method for coding a 3D video including a depth-map picture,
the method comprising: deriving a first index value with respect to
a first sample of a current block by mapping a predicted depth
value of the first sample of the current block on a depth lookup
table (DLT), wherein predicted depth value of the first sample has
been induced based on an intra-prediction mode of the current block
in a depth-map picture; deriving a second index value with respect
to the first sample of the current block by mapping an original
depth value of the first sample of the current block on the DLT;
deriving a residual index value between the first index value and
the second index value with respect to the first sample of the
current block; and transforming, quantizing, and entropy-coding the
residual index value.
2. The method of claim 1, wherein: the size of the current block is
2N.times.2N, and the current block includes 2N.times.2N
samples.
3. The method of claim 1, wherein the intra prediction mode of the
current block is any one of a DC mode, a vertical mode, a
horizontal mode, and a depth map intra prediction mode.
4. The method of claim 1, wherein the DLT is a lookup table
generated by mapping the depth value of the depth-map picture to
the index value.
5. The method of claim 4, wherein in the DLT, the depth value of an
i-th index is derived based on a difference between the depth value
of the i-th index and a depth value of an (i-1)-th index in the
DLT.
6. A method for decoding a 3D video including a depth-map picture,
the method comprising: acquiring a residual index value for a
current block in the depth-map picture through entropy-decoding,
dequantization, and inverse transformation; deriving a predicted
depth value of a first sample in the current block based on an
intra prediction mode of the current block; deriving a first index
value for the first sample in the current blocking by mapping the
predicted depth value of the first sample of the current block on a
DLT; and acquiring the depth value of the first sample of the
current block by adding the first index value and the residual
index value with respect to the first sample of the current block,
wherein the depth value of the first sample of the current block is
a value acquired by mapping a second index value derived by adding
the first index value and the residual index value to the DLT.
7. The method of claim 6, wherein: the size of the current block is
2N.times.2N, and the current block includes 2N.times.2N
samples.
8. The method of claim 6, wherein the intra prediction mode of the
current block is any one of a DC mode, a vertical mode, a
horizontal mode, and a depth map intra prediction mode.
9. The method of claim 6, wherein the DLT is a lookup table
generated by mapping the depth value of the depth-map picture to
the index value.
10. The method of claim 9, wherein in the DLT, the depth value of
an i-th index is derived based on a difference between the depth
value of the i-th index and a depth value of an (i-1)-th index in
the DLT.
11. An encoding apparatus for coding a 3D video including a
depth-map picture, the apparatus comprising: a prediction unit
configured to induce a predicted depth value of the first sample
based on an intra-prediction mode of a current block in a depth-map
picture; a subtraction unit configured to derive a first index
value with respect to the first sample of the current block by
mapping the predicted depth value of the first sample of the
current block on a depth lookup table (DLT), derive a second index
value with respect to the first sample of the current block by
mapping an original depth value of the first sample of the current
block on the DLT, and derive a residual index value between the
first index value and the second index value with respect to the
first sample of the current block; a transform unit configured to
perform transform on the residual index value; a quantization unit
configured to perform quantization on a result of the transform;
and a entropy encoding unit configured to perform entropy encoding
on a result of the quantization.
12. The apparatus of claim 11, wherein: the size of the current
block is 2N.times.2N, and the current block includes 2N.times.2N
samples.
13. The apparatus of claim 11, wherein the intra prediction mode of
the current block is any one of a DC mode, a vertical mode, a
horizontal mode, and a depth map intra prediction mode.
14. The apparatus of claim 11, wherein the DLT is a lookup table
generated by mapping the depth value of the depth-map picture to
the index value.
15. The apparatus of claim 14, wherein in the DLT, the depth value
of an i-th index is derived based on a difference between the depth
value of the i-th index and a depth value of an (i-1)-th index in
the DLT.
16. A decoding apparatus for decoding a 3D video including a
depth-map picture, the apparatus comprising: an entropy decoding
unit configured to perform entropy-decoding on information on a
residual index value for a current block in the depth-map picture;
a dequantization unit configured to acquire a residual index value
for the current block in the depth-map picture by performing
dequantization on a result of the entropy-decoding; an inverse
transform unit configured to perform invers transform on a result
of the dequantization; a prediction unit configured to derive a
predicted depth value of a first sample in the current block based
on an intra prediction mode of the current block; an adding unit
configured to derive a first index value for the first sample in
the current block by mapping the predicted depth value of the first
sample of the current block on a DLT, and acquire the depth value
of the first sample of the current block by adding the first index
value and the residual index value with respect to the first sample
of the current block, wherein the depth value of the first sample
of the current block is a value acquired by mapping a second index
value derived by adding the first index value and the residual
index value to the DLT.
17. The apparatus of claim 16, wherein: the size of the current
block is 2N.times.2N, and the current block includes 2N.times.2N
samples.
18. The apparatus of claim 16, wherein the intra prediction mode of
the current block is any one of a DC mode, a vertical mode, a
horizontal mode, and a depth map intra prediction mode.
19. The apparatus of claim 16, wherein the DLT is a lookup table
generated by mapping the depth value of the depth-map picture to
the index value.
20. The apparatus of claim 19, wherein in the DLT, the depth value
of an i-th index is derived based on a difference between the depth
value of the i-th index and a depth value of an (i-1)-th index in
the DLT.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a technology associated
with video coding, and more particularly, to coding of a 3D video
picture.
[0003] 2. Related Art
[0004] In recent years, demands for a high-resolution and
high-quality video have increased in various fields of
applications. However, the higher the resolution and quality video
data becomes, the greater the amount of video data becomes.
[0005] Accordingly, when video data is transferred using media such
as existing wired or wireless broadband lines or video data is
stored in existing storage media, the transfer cost and the storage
cost thereof increase. High-efficiency video compressing techniques
can be used to effectively transfer, store, and reproduce
high-resolution and high-quality video data.
[0006] On the other hand, with realization of capability of
processing a high-resolution/high-capacity video, digital broadcast
services using a 3D video have attracted attention as a
next-generation broadcast service. A 3D video can provide a sense
of realism and a sense of immersion using multi-view channels.
[0007] A 3D video can be used in various fields such as free
viewpoint video (FVV), free viewpoint TV (FTV), 3DTV, surveillance,
and home entertainments.
[0008] Unlike a single-view video, a 3D video using multi-views
have a high correlation between views having the same picture order
count (POC). Since the same scene is shot with multiple neighboring
cameras, that is, multiple views, multi-view videos have almost the
same information except for a parallax and a slight illumination
difference and thus difference views have a high correlation
therebetween.
[0009] Accordingly, the correlation between different views can be
considered for coding/decoding a multi-view video, and information
need for coding and/or decoding of a current view can be obtained.
For example, a block to be decoded in a current view can be
predicted or decoded with reference to a block in another view.
SUMMARY OF THE INVENTION
[0010] The present invention provides a method and an apparatus for
coding/decoding a 3D video including a depth-map picture.
[0011] The present invention provides a method and an apparatus for
coding/decoding a 3D video including a depth lookup table.
[0012] In one aspect, a method for coding a 3D video including a
depth-map picture is provided. The method for coding a 3D video
includes: deriving a first index value with respect to a first
sample of a current block by mapping a predicted depth value of the
first sample of the current block on a depth lookup table (DLT),
wherein the predicted depth value of the first sample has been
induced based on an intra-prediction mode of the current block in a
depth-map picture; deriving a second index value with respect to
the first sample of the current block by mapping an original depth
value of the first sample of the current block on the DLT; deriving
a residual index value between the first index value and the second
index value with respect to the first sample of the current block;
and transforming, quantizing, and entropy-coding the residual index
value.
[0013] In another aspect, a method for decoding a 3D video
including a depth-map picture is provided. The method for decoding
a 3D video includes: acquiring a residual index value for a current
block in the depth-map picture through entropy-decoding,
dequantization, and inverse transformation; deriving a predicted
depth value of a first sample in the current block based on an
intra prediction mode of the current block; deriving a first index
value for the first sample in the current blocking by mapping the
predicted depth value of the first sample of the current block on a
DLT; and acquiring the depth value of the first sample of the
current block by adding the first index value and the residual
index value with respect to the first sample of the current
block.
[0014] The depth value of the first sample of the current block may
be a value acquired by mapping a second index value derived by
adding the first index value and the residual index value to the
DLT.
[0015] According to the present invention, coding and decoding are
performed by using a depth lookup table (DLT) to reduce
complexities of an encoder and a decoder and improve
coding/decoding efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a diagram scheduling describing encoding and
decoding processes of a 3D video.
[0017] FIG. 2 is a diagram schematically describing a configuration
of a video encoding apparatus.
[0018] FIG. 3 is a diagram schematically describing a configuration
of a video decoding apparatus.
[0019] FIG. 4 is a diagram for schematically describing an intra
prediction method of a depth map in a depth modeling mode
(DMM).
[0020] FIG. 5 is a flowchart schematically illustrating a method
for encoding by applying intra prediction using a DLT according to
an embodiment of the present invention.
[0021] FIG. 6 is a flowchart schematically illustrating a method
for selecting an optimal intra prediction mode according to an
embodiment of the present invention.
[0022] FIG. 7 is a flowchart schematically illustrating a method
for decoding by applying intra prediction using a DLT according to
an embodiment of the present invention.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0023] The invention may be variously modified in various forms and
may have various embodiments, and specific embodiments thereof will
be illustrated in the drawings and described in detail. However,
these embodiments are not intended for limiting the invention.
Terms used in the below description are used to merely describe
specific embodiments, but are not intended for limiting the
technical spirit of the invention. An expression of a singular
number includes an expression of a plural number, so long as it is
clearly read differently. Terms such as "include" and "have" in
this description are intended for indicating that features,
numbers, steps, operations, elements, components, or combinations
thereof used in the below description exist, and it should be thus
understood that the possibility of existence or addition of one or
more different features, numbers, steps, operations, elements,
components, or combinations thereof is not excluded.
[0024] On the other hand, elements of the drawings described in the
invention are independently drawn for the purpose of convenience of
explanation on different specific functions, and do not mean that
the elements are embodied by independent hardware or independent
software. For example, two or more elements out of the elements may
be combined to form a single element, or one element may be split
into plural elements. Embodiments in which the elements are
combined and/or split belong to the scope of the invention without
departing from the concept of the invention.
[0025] In the specification, a pixel or a pel may mean a minimum
unit constituting one picture. Further, a `sample` may be used as a
term indicating a value of a specific pixel. The sample generally
indicates the pixel of the pixel, but may indicate only a pixel
value of a luminance (luma) component or indicate only a pixel
value of a chroma component.
[0026] A unit may mean a base unit of picture processing or a
specific position of a picture. The unit may be used mixedly with a
term such as a block or an area in some cases. In a general case,
an M.times.N block may indicate a set of samples constituted by M
columns and N rows or transform coefficients.
[0027] FIG. 1 is a diagram scheduling describing encoding and
decoding processes of a 3D video.
[0028] Referring to FIG. 1, a 3 video encoder encodes a video
picture and a depth and a camera parameter to output the same as a
bitstream.
[0029] The depth map may be constituted by distance information
(depth information) between a camera and a subject with respect to
a pixel of the corresponding video picture (texture picture). For
example, the depth map may be a picture acquired by normalizing the
depth information according to a bit depth. In this case, the depth
map may be constituted by the depth information recorded without
expression of a chrominance.
[0030] In general, since a distance from the subject and a
disparity are in inverse proportion to each other, disparity
information indicating a correlation between views may be induced
from the depth information of the depth map by using the camera
parameter.
[0031] A bitstream including the depth map and camera information
together with a general color picture, that is, the video picture
(texture picture) may be transmitted to a decoder through a network
or a storage medium.
[0032] The decoder receives the bitstream to reconstruct the video.
When a 3D video decoder is used as the decoder, the 3D video
decoder may decode the video picture, and the depth map and the
camera parameter from the bitstream. Views required for a
multi-view display may be synthesized based on the decoded video
picture, depth map, and camera parameter. In this case, when the
used display is a stereo display, the 3D picture may be displayed
by using two pictures among the reconstructed multi-views.
[0033] When the stereo video decoder is used, the stereo video
decoder may reconstruct two pictures to be incident in both eyes
from the bitstream. The stereo display may display a 3D picture by
using a view difference or disparity between a left picture
incident in a left eye and a right picture incident in a right eye.
When the multi-view display is used together with the stereo video
decoder, the multi-views may be displayed by generating other views
based on the two reconstructed pictures.
[0034] When a 2D decoder is used, a 2D picture is reconstructed to
output the picture through a 2D display. The 2D display is used,
but when the 3D video decoder or the stereo video decoder is used
as the decoder, one of the reconstructed pictures may be output
through the 2D display.
[0035] In the configuration of FIG. 1, the view synthesis may be
performed by the decoder or the display. Further, the decoder and
the display may be one apparatus or separate apparatuses.
[0036] In FIG. 1, for easy description, it is described that the 3D
video decoder, the stereo video decoder, and the 2D video decoder
are separate decoders, but one decoding apparatus may perform all
3D video decoding, stereo video decoding, and 2D video decoding.
Further, a 3D video decoding apparatus may perform the 3D video
decoding, a stereo video decoding apparatus may perform the stereo
video decoding, and a 2D video decoding apparatus may perform the
2D video decoding. Furthermore, the multi-view display may output a
2D video or a stereo video.
[0037] FIG. 2 is a diagram schematically describing a configuration
of a video encoding apparatus.
[0038] Referring to FIG. 2, the video encoding apparatus 200
includes a picture splitting unit 205, a prediction unit 210, a
subtraction unit 215, a transform unit 220, a quantization unit
225, a reordering unit 230, an entropy encoding unit 235, an
dequantization unit 240, an inverse transform unit 245, an adding
unit 250, a filter unit 255, and a memory 260.
[0039] The picture splitting unit 05 may split an input picture
into at least one processing unit block. In this case, the
processing unit block may be a coding unit block, a prediction unit
block, or a transform unit block. The coding unit block as a unit
block of coding may be split from a maximum coding unit block
according to a quad tree structure. The prediction unit block as a
block partitioned from the coding unit block may be a unit block of
sample prediction. In this case, the prediction unit block may be
divided into sub blocks. The transform unit bock as the coding unit
block may be split according to the quad tree structure and may be
a unit block to induce a transform coefficient or a unit block to
induce a residual signal from the transform coefficient.
[0040] Hereinafter, for easy description, the coding unit block is
referred to as a coding block or a coding unit, and the prediction
unit block is referred to as a prediction block or a prediction
unit, and the transform unit block is referred to as a
transformation block or a transform unit.
[0041] The prediction block or the prediction unit may mean a
block-shape specific area or an array of the prediction sample.
Further, the transformation block or the transform unit may mean
the block-shape specific area or an array of the transform
coefficient or a residual sample.
[0042] The prediction unit 210 may perform a prediction for a
processing target block (hereinafter, referred to as a current
block) and generate the prediction block including prediction
samples for the current block. A unit of the prediction performed
by the prediction unit 210 may be the coding block, the
transformation block, or the prediction block.
[0043] The prediction unit 210 may decide whether an intra
prediction is applied to the current block or whether an inter
prediction is applied to the current block.
[0044] In the case of the intra prediction, the prediction unit 210
may induce the prediction sample for the current block based on a
neighbor block pixel in a picture (hereinafter, a current picture)
to which the current block belongs. In this case, the prediction
unit 210 may (i) induce the prediction sample based an average or
an interpolation of neighbor reference samples of the current block
or (ii) induce the prediction sample based on a reference sample
which is present in a specific direction with respect to a
prediction target pixel among neighbor blocks of the current block.
For easy description, the case of (i) is referred to as a
non-directional mode and the case of (ii) is referred to as a
directional mode. The prediction unit 210 may decide a prediction
mode applied to the current block by using the prediction mode
applied to the neighbor block.
[0045] In the case of the inter prediction, the prediction unit 210
may induce the prediction sample for the current block based on
samples specified by a motion vector on a collocated picture. The
prediction unit 10 applies any one of a skip mode, a merge mode,
and an MVP mode to induce the prediction sample for the current
block. In the cases of the skip mode and the merge mode, the
prediction unit 210 may use motion information of the neighbor
block as the motion information of the current block. In the case
of the skip mode, a difference (residual) between the prediction
sample and an original sample is not transmitted unlike the merge
mode. In the case of the MVP mode, the motion vector of the
neighbor block is used as a motion vector predictor (MVP) to induce
the motion vector of the current block.
[0046] In the case of the inter prediction, the neighbor block
includes a spatial neighbor block which is present in the current
picture and a spatial neighbor block which is present in the
collocated picture. The motion information includes the motion
vector and the collocated picture. In the skip mode and the merge
mode, when the motion information of the spatial neighbor block is
used, a highest picture on a collocated picture list may be used as
the collocated picture.
[0047] In the case of encoding a dependent view, the prediction
unit 210 may perform an inter-view prediction.
[0048] The prediction unit 210 may configure the collocated picture
list including a picture of another view. For the inter-view
prediction, the prediction unit 210 may induce a disparity vector.
Unlike a motion vector specifying a block corresponding to the
current block in another picture in a current view, the disparity
vector may specify a block corresponding to the current block in
another view of the same access unit as the current picture.
[0049] The prediction unit 10 may specify a depth block in a depth
view based on the disparity vector and perform a configuration of a
merge list, an inter-view motion prediction, an illumination
compensation (IC), view synthesis, and the like.
[0050] The disparity vector for the current block may be induced
from a depth value by using the camera parameter or induced from
the motion vector or disparity vector of the neighbor block in the
current or another view.
[0051] For example, the prediction unit 210 may add to a merge
candidate list an inter-view merging candidate (IvMC) corresponding
to spatial motion information of a reference view, an inter-view
disparity vector candidate (IvDC) corresponding to the disparity
vector, a shifted IvMC induced by a shift of the disparity, a
texture merging candidate (T) induced from a texture corresponding
to a case in which the current block is a block on the depth map, a
disparity derived merging candidate (D) derived from the texture
merging candidate by using the disparity, a view synthesis
prediction merge candidate (VSP) derived based on the view
synthesis, and the like.
[0052] In this case, the number of candidates included in a merge
candidate list applied to the dependent view may be limited to a
predetermined value.
[0053] Further, the prediction unit 210 may predict the motion
vector of the current block based on the disparity vector by
applying the inter-view motion vector prediction. In this case, the
prediction unit 210 may derive the disparity vector based on
conversion of a maximum depth value in the corresponding depth
block. When a position of the reference sample in the reference
view is specified by adding the disparity vector to a sample
position of the current block in the reference view, a block
including the reference sample may be used as the reference block.
The prediction unit 210 may use the motion vector of the reference
block as a candidate motion parameter or a motion vector predictor
candidate of the current block and use the disparity vector as a
candidate disparity vector for the DCP.
[0054] The subtraction unit 215 generates the residual sample which
is the difference between the original sample and the prediction
sample. When the skip mode is applied, the subtraction unit 215 may
not generate the residual sample as described above.
[0055] The transform unit 210 generates the transform coefficient
by using transforming the residual sample by the unit of the
transform block. The quantization unit 225 quantizes the transform
coefficients to generate quantized transform coefficients.
[0056] The reordering unit 230 reorders the quantized transform
coefficients. The reordering unit 230 may reorder the block-shape
quantized transform coefficients in a 1D vector shape through a
scanning method.
[0057] The entropy encoding unit 235 may perform entropy-encoding
of the quantized transform coefficients. As the entropy encoding,
encoding methods including, for example, exponential Golomb,
context-adaptive variable length coding (CAVLC), context-adaptive
binary arithmetic coding (CABAC), and the like may be used. The
entropy encoding unit 235 may encode information (e.g., a value of
a syntax element, and the like) required for video reconstruction
together or separately in addition to the quantized transform
coefficients.
[0058] The entropy-encoded information may be transmitted or stored
by the unit of a network abstraction layer as the form of the
bitstream.
[0059] The dequantization unit 240 dequantizes the quantized
transform coefficient to generate the transform coefficient. The
inverse transform unit 245 inversely transforms the transform
coefficient to generate the residual sample.
[0060] The adding unit 250 adds the residual sample and the
prediction sample to reconstruct the picture. The residual sample
and the prediction sample are added to each other by the unit of
the block to generate a reconstruction block. Herein, the adding
unit 250 is described as a separate component, but the adding unit
250 may be a part of the prediction unit 210.
[0061] The filter unit 255 may apply a deblocking filter and/or
offset to the reconstructed picture. Distortion during an artifact
or a quantization process of a block boundary in the reconstructed
picture may be corrected through the deblocking filtering and/or
offset. The offset may be applied by the unit of the sample and
applied after the process of the deblocking filtering is
completed.
[0062] The memory 260 may store the reconstructed picture or
information required for encoding/decoding. For example, the memory
60 may store pictures used for the inter prediction/inter-view
prediction. In this case, the pictures used for the inter
prediction/inter-view prediction may be designated by a collocated
picture set or a collocated picture list.
[0063] Herein, it is described that one encoding apparatus encodes
an independent view or the dependent view, but this is for easy
description and a separate encoding apparatus is configured for
each view or a separate internal module (for example, a prediction
unit for each view) may be configured for each view.
[0064] FIG. 3 is a diagram schematically describing a configuration
of a video decoding apparatus.
[0065] Referring to FIG. 3, the video decoding apparatus 300
includes an entropy decoding unit 310, a reordering unit 320, a
dequantization unit 330, an inverse transform unit 340, a
prediction unit 350, an adding unit 360, a filter unit 370, and a
memory 380.
[0066] When a bitstream including video information is input, the
video decoding apparatus 300 may reconstruct a video to correspond
to a process in which the video information is processed by the
video encoding apparatus.
[0067] For example, the video decoding apparatus 300 may perform
video decoding by using the processing unit applied in the video
encoding apparatus. In this case, the processing unit block of the
video decoding may be the coding unit block, the prediction unit
block, or the transform unit block. The coding unit block as a unit
block of decoding may be split from the maximum coding unit block
according to the quad tree structure. The prediction unit block as
the block partitioned from the coding unit block may be the unit
block of sample prediction. In this case, the prediction unit block
may be divided into sub blocks. The transform unit bock as the
coding unit block may be split according to the quad tree structure
and may be a unit block to derive a transform coefficient or a unit
block to derive a residual signal from the transform
coefficient.
[0068] The entropy decoding unit 310 parses the bitstream to output
information required for video reconstruction or picture
reconstruction. For example, the entropy decoding unit 310 may
decode information in the bitstream based on the exponential
Golomb, the CAVLC, the CABAC, and the like and output the value of
the syntax element required for the video reconstruction, the
quantized value of the transform coefficient associated with the
residual, and the like.
[0069] When a plurality of views is processed in order to reproduce
the 3D video, the bitstream may be input for each view.
Alternatively, information on the respective views may be
multiplexed in the bitstream. In this case, the entropy decoding
unit 310 de-multiplexes the bitstream to parse the de-multiplexed
bitstream for each view.
[0070] The reordering unit 320 may reorder the quantized transform
coefficients in the 2D block form. The reordering unit 320 may
perform reordering to correspond to coefficient scanning performed
by the encoding apparatus.
[0071] The dequantization unit 330 dequantizes the quantized
transform coefficients based on (de)quantized parameters to output
the transform coefficients. Information for deriving the quantized
parameters may be signaled from the encoding apparatus.
[0072] The inverse transform unit 340 inversely transforms the
transform coefficients to derive the residual samples.
[0073] The prediction unit 350 may perform a prediction for the
current block and generate the prediction block including
prediction samples for the current block. A unit of the prediction
performed by the prediction unit 350 may be the coding block, the
transformation block, or the prediction block.
[0074] The prediction unit 350 may decide whether the intra
prediction is applied to the current block or whether the inter
prediction is applied to the current block. In this case, a unit
for deciding which the intra prediction or the inter prediction is
applied and a unit for generating the prediction sample may be
different from each other. Moreover, the units for generating the
prediction sample in the inter prediction and the intra prediction
may also be different from each other.
[0075] In the case of the intra prediction, the prediction unit 350
may derive the prediction sample for the current block based on the
neighbor block pixel in the current picture. The prediction unit
350 may derive the prediction sample for the current block by
applying the directional mode or the non-directional mode based on
neighbor reference blocks of the current block. In this case, the
prediction mode to be applied to the current block may be decided
by using an intra prediction mode of the neighbor block.
[0076] In the case of the inter prediction, the prediction unit 350
may derive the prediction sample for the current block based on the
samples specified by the motion vector on the collocated picture.
The prediction unit 10 applies any one of the skip mode, the merge
mode, and the MVP mode to derive the prediction sample for the
current block.
[0077] In the cases of the skip mode and the merge mode, the
prediction unit 350 may use the motion information of the neighbor
block as the motion information of the current block. In this case,
the neighbor block may include a spatial neighbor block and a
temporal neighbor block.
[0078] The prediction unit 350 may configure the merge candidate
list as motion information of an available neighbor block and
information indicated by a merge index on the merge candidate list
may be used as the motion vector of the current block. The merge
index may be signaled from the encoding apparatus. The motion
information includes the motion vector and the collocated picture.
In the skip mode and the merge mode, when the motion information of
the temporal neighbor block is used, the highest picture on the
collocated picture list may be used as the collocated picture.
[0079] In the case of the skip mode, the difference (residual)
between the prediction sample and the original sample is not
transmitted unlike the merge mode.
[0080] In the case of the MVP mode, the motion vector of the
neighbor block is used as the motion vector predictor (MVP) to
derive the motion vector of the current block. In this case, the
neighbor block may include the spatial neighbor block and the
temporal neighbor block.
[0081] In the case of encoding the dependent view, the prediction
unit 350 may perform the inter-view prediction. In this case, the
prediction unit 350 may configure the collocated picture list
including the picture of another view.
[0082] For the inter-view prediction, the prediction unit 350 may
derive the disparity vector. The prediction unit 350 may specify
the depth block in the depth view based on the disparity vector and
perform the configuration of the merge list, the inter-view motion
prediction, the illumination compensation (IC), the view synthesis,
and the like.
[0083] The disparity vector for the current block may be derived
from the depth value by using the camera parameter or derived from
the motion vector or disparity vector of the neighbor block in the
current or another view. The camera parameter may be signaled from
the encoding apparatus.
[0084] When the merge mode is applied to the current block of the
dependent view, the prediction unit 350 may add to the merge
candidate list IvDC corresponding to the temporal motion
information of the reference view, IvDC corresponding to the
disparity vector, shift IvMC derived by the shift of the disparity
vector, the texture merge candidate (T), derived from the texture
corresponding to the case in which the current block is the block
on the depth map, the disparity derive merge candidate (D) derived
from the texture merge candidate by using the disparity, the view
synthesis prediction merge candidate (VSP) derived based on the
view synthesis, and the like.
[0085] In this case, the number of candidates included in the merge
candidate list applied to the dependent view may be limited to a
predetermined value.
[0086] Further, the prediction unit 350 may predict the motion
vector of the current block based on the disparity vector by
applying the inter-view motion vector prediction. In this case, the
prediction unit 350 may use the block in the reference view
specified by the disparity vector as the reference block. The
prediction unit 350 may use the motion vector of the reference
block as the candidate motion parameter or the motion vector
predictor candidate of the current block and use the disparity
vector as the candidate disparity vector for the DCP.
[0087] The adding unit 360 adds the residual sample and the
prediction sample to reconstruct the current block or the current
picture. The adding unit 360 adds the residual sample and the
prediction sample by the unit of the block to reconstruct the
current picture. When the skip mode is applied, since the residual
is not transmitted, the prediction sample may become a
reconstruction sample. Herein, the adding unit 360 is described as
a separate component, but the adding unit 360 may be a part of the
prediction unit 350.
[0088] The filter unit 370 may apply the deblocking filtering
and/or offset to the reconstructed picture. In this case, the
offset may be adaptively applied as the offset of the sample
unit.
[0089] The memory 380 may store the reconstructed picture or
information required for decoding. For example, the memory 380 may
store pictures used for the inter prediction/inter-view prediction.
In this case, the pictures used for the inter prediction/inter-view
prediction may be designated by the collocated picture set or the
collocated picture list. The reconstructed picture may be used as
the collocated picture.
[0090] Further, the memory 380 may output the reconstructed
pictures according to an output order. In order to reproduce the 3D
picture, although not illustrated, an output unit may display a
plurality of different views.
[0091] In the example of FIG. 3, it is described that one decoding
apparatus decodes the independent view and the dependent view, but
this is for easy description and the present invention is not
limited thereto. For example, each decoding apparatus may operate
for each view and one decoding apparatus may include an operating
unit (for example, a prediction unit) corresponding to each view
therein.
[0092] Meanwhile, the 3D video includes a texture video having
general color picture information and a depth-map video having
depth information for the texture video.
[0093] The depth-map video stores a distance possessed by each
pixel of the picture as a gray scale and a minute depth difference
among the respective pixels is not severe in one block and there
are many cases in which the depth map video may be expressed as two
kinds of a foreground and a background. Further, the depth map
video shows a characteristic in which the depth map video has a
sharp edge on a boundary of an object and has an almost constant
value (constant value) at a location other than the boundary.
[0094] Since the intra prediction used to the existing texture
video is a prediction method suitable for a constant area having a
predetermined value, the intra prediction is not effective to
predict the depth map having a different characteristic from the
texture video.
[0095] Therefore, a new intra prediction mode reflecting the
characteristic of the depth map is added in the 3D video coding. In
the intra prediction mode for the depth map, the depth map block
(alternatively, depth block) is expressed as a model split into two
non-rectangular areas and each of the split areas is expressed as
the constant value.
[0096] As described above, the intra prediction mode to express and
predict the depth map block as one model is referred to as a depth
modeling mode (DMM). In the DMM, the depth map may be predicted
based on partition information indicating how the depth map block
is split and information on a value filled in each partition.
[0097] FIG. 4 is a diagram for schematically describing an intra
prediction method of a depth map in a depth modeling mode
(DMM).
[0098] Referring to FIG. 4, when a depth block 400 which becomes an
intra prediction target in the depth-map picture is intra-predicted
by the DMM, the depth block 400 may be split into two
non-rectangular areas P.sub.1 and P.sub.2. The split areas P.sub.1
and P.sub.2 are filled with constant values, respectively.
[0099] In this case, as an optimal constant value filling each of
the split areas, an average value of original depth values of the
respective areas may be used. However, an encoder does not signal
the average value of the original depth values but averages values
of neighbor samples adjacent to the respective areas to acquire a
prediction value and a difference .DELTA.W between the prediction
value W.sub.pred and the average value W.sub.orig of the original
depth values is calculated to signal the residual value .DELTA.W. A
decoder may reconstruct each area based on the signaled residual
value .DELTA.W of the respective areas and the prediction value
W.sub.pred of each area.
[0100] For example, the encoder averages the values of the neighbor
samples adjacent the area P1 to acquire a prediction value
W.sub.predP1 of the area P.sub.1 and calculate a difference
.DELTA.W.sub.P1 between the prediction value W.sub.predP1 of the
area P.sub.1 and an average value W.sub.origP1 of original depth
values of the area P.sub.1. The encoder may transmit the calculated
difference .DELTA.W.sub.P1 of the area P1 to the decoder.
[0101] The decoder averages the values of the neighbor samples
adjacent to the area P1 to acquire the prediction value
W.sub.predP1 of the area P.sub.1 and adds the difference
.DELTA.W.sub.P1 of the area P.sub.1, which is transmitted from the
encoder to the prediction value W.sub.predP1 of the area P.sub.1 to
reconstruct the area P.sub.1.
[0102] By the same method as the area P.sub.1, a prediction value
W.sub.predP2 of the area P.sub.2 may be derived by using values of
neighbor samples adjacent to the area P.sub.2 and a difference
.DELTA.W.sub.P2 between the prediction value W.sub.predP2 of an the
area P.sub.2 and an average value W.sub.origP2 of original depth
values of the area P.sub.2 may be calculated. The decoder may
reconstruct the area P.sub.2 based on the values.
[0103] When the depth-map picture is coded in the 3D video coding,
a residual block may be coded by using a lookup table. In general,
values of sample (pixel) values of the depth-map picture are not
evenly distributed and are distributed concentratively on a
specific area. When the lookup table is generated by considering
such a characteristic and the depth value of the depth-map picture
is transformed into an index value of the lookup table to be
encoded, the number of bits to be encoded may be reduced. Further,
the residual block generated by using the lookup table may be
entropy-coded without the transformation and quantization
processes. Therefore, a coding method of the depth-map picture
using the lookup table is referred to as simplified depth coding
(SDC).
[0104] In the SDC method, the prediction is performed by using the
aforementioned depth modeling mode (DMM) and a planar mode unlike
the existing intra prediction and residual data generated based on
the predicted data are indexed by using a predetermined lookup
table without the transformation and quantization processes.
[0105] Hereinafter, the SDC method that codes the residual block by
using the lookup table will be described in more detail.
[0106] A block (hereinafter, referred to as a current block) to be
coded currently in the depth-map picture may be intra-predicted by
using the DMM or the planar mode. In this case, in the case of the
intra prediction using the DMM, as described above, the current
block is split into two areas and an average of depth values
predicted with respect to the respective areas are acquired to be
used as a prediction value. In the case of the intra prediction
using the planar mode, since the current block may be one area
which is not split, an average of depth values predicted with
respect to one area in the current block is acquire to be used as
the prediction value.
[0107] That is, the average of the depth value intra predicted with
respect to the respective split areas (in the case of the DMM, two
areas and in the case of the planar, one area) in the current block
and an average of original depth values are calculated and the
respective calculated average values are mapped to the lookup table
to find each index value. In addition, instead of encoding a
residual value between the original depth value and the predicted
depth value, a residual value between an index of the average of
the original depth value mapped from the lookup table and the
average of the predicted depth value may be encoded.
[0108] Equation 1 given below shows a process of generating a
difference index value for the current block by the SDC method.
Res_indexi=DLT[Orgi_DC]-DLT[Predi_DC] [Equation 1]
[0109] In Equation 1, i represents the split area in the current
block and depth lookup table (DLT) represents a lookup table for a
previously generated depth value.
[0110] Since the SDC method generates the residual signal by using
the average of the prediction value with respect to the split area
as described above, the SDC method is also referred to as
segment-wise DC coding.
[0111] In the aforementioned SDC method, the intra prediction is
performed and the residual signal is generated by using the lookup
table (hereinafter, referred to as the DLT) for the depth value in
the SDC mode (the DMM and the planar mode).
[0112] Hereinafter, the present invention proposes the SDC method
that uses the DLT even in the intra prediction mode used to predict
the texture video in addition to the SDC mode.
[0113] The intra prediction mode used to predict the texture video
may include a directional mode and a non-directional mode according
to directions in which the reference samples used to predict the
sample value of the current block and/or a prediction scheme. For
example, the intra prediction mode may include 33 directional
prediction modes and at least two non-directional prediction
modes.
[0114] The non-directional prediction mode may include a DC mode
and the planar mode. The DC mode may use one fixed value as
prediction values of samples in the current block. As one example,
in the DC mode, one fixed value may be derived by an average of
sample values positioned around the current block. The planar mode
may perform vertical interpolation and horizontal interpolation by
using a sample vertically adjacent to the current block and a
sample horizontally adjacent to the current block and use an
average value of the vertical and horizontal interpolation values
as the prediction values of the samples in the current block.
[0115] The directional prediction mode as a mode indicating a
direction in which the reference sample is positioned indicate the
corresponding direction at an angle between a prediction target
sample in the current block and the reference sample. The
directional prediction mode may be referred to as an angular mode
and include a vertical mode, a horizontal mode, and the like. The
vertical mode may use the sample value vertically adjacent to the
current block as the prediction value of the sample in the current
block and the horizontal mode may use the sample value horizontally
adjacent to the current block as the prediction value of the sample
in the current block. In addition, the residual angular mode other
than the vertical mode and the horizontal mode may deduce the
prediction value of the sample in the current block by using the
reference sample positioned at a predetermined angle and/or in a
predetermined direction with each mode.
[0116] In the intra prediction using the existing intra prediction
mode (35 intra prediction modes used to predict the texture video),
the residual signal is generated by the unit of the pixel (sample)
with respect to one block and the residual signal goes through the
transformation and quantization processes and thereafter, is
entropy-encoded. However, the intra prediction method using the DLT
proposed by the present invention, the DLT is applied to each pixel
of an original picture and each pixel of a prediction picture and
thereafter, the residual signal is generated by the residual value
of the index mapped to the DLT and the residual signal goes through
the transformation and quantization processes and thereafter, is
entropy-encoded. Therefore, an area of the residual signal
generated based on the existing intra prediction is a value area,
but an area of the residual signal generated through the intra
prediction using the DLT proposed by the present invention is an
index area.
[0117] Further, in the existing SDC mode, the DLT is applied by the
unit of the split area in one block to derive the index residual
value, but in the present invention, the DLT is applied by the unit
of the pixel in the block to derive the index residual value.
Therefore, when the method proposed by the present invention is
used, accuracy of the prediction may further increase and a
reconstruction picture close to the original picture may be
generated.
[0118] FIG. 5 is a flowchart schematically illustrating a method
for encoding by applying intra prediction using a DLT according to
an embodiment of the present invention. The method of FIG. 5 may be
performed by the video encoding apparatus of FIG. 2.
[0119] Referring to FIG. 5, the encoding apparatus performs the
prediction based on the intra prediction mode of the block
(hereinafter, referred to as the current block) to encoded
currently in the depth-map picture to a predicted depth value of
each sample in the current block. In addition, the encoding
apparatus maps the depth lookup table (DLT) to the derived
predicted depth value of each sample of the current block to derive
an index value of each DLT (S500).
[0120] Herein, the intra prediction mode may be any one of the
aforementioned existing intra prediction mode (35 intra prediction
modes used to predict the texture video) and a depth map intra
prediction mode (the SDC mode including the DMM).
[0121] The DLT as the lookup table storing the depth value of the
depth-map picture has information in which each depth value is
mapped to the index value. In general, values of sample (pixel)
values of the depth-map picture are not evenly distributed and are
distributed concentratively on a specific area. The index of the
DLT may be generated by considering such a feature and the depth
value of the depth-map picture may be mapped to (transformed into)
the index value.
[0122] For example, in the DLT, a depth value of an i-th index may
be derived based on a difference between the depth value of the
i-th index and a depth value of an (i-1)-th index in the DLT.
Therefore, the encoding apparatus may signal the difference between
the depth value of the i-th index and the depth value of the
(i-1)-th index to the decoding apparatus. The decoding apparatus
may derive the depth values in the DLT based on the signal residual
value.
[0123] The encoding apparatus maps the DLT to the original depth
value of each sample of the current block to derive the index value
of each DLT (S510).
[0124] The encoding apparatus derives a residual index between the
index of the depth value predicted with respect to each sample of
the current block and the index of the original depth value
(S520).
[0125] The encoding apparatus may use the residual index value for
each sample of the current block as the residual signal.
[0126] Equation shows a process of deriving the residual signal
according to the embodiment of the present invention.
Res_index[x]=DLT[Org[x]]-DLT[Pred[x]] [Equation 2]
[0127] In Equation 2, x represents each sample in the current
block. Org[x] represents the original depth value of a sample x in
the current block and Pred[x] represents the predicted depth value
of the sample x in the current block. DLT[Org[x]] represents
transformation of the original depth value of the sample x in the
current block into the index value and DLT[Pred[x]] represents
transformation of the predicted depth value of the sample x in the
current block into the index value of the DLT. Res_index[x]
represents the residual index value of the sample x in the current
block.
[0128] For example, the encoding apparatus maps the DLT to a
predicted depth value Pred[x.sub.1] of a first sample in the
current block, which is derived based on the intra prediction mode
of the current block to derive a first index value
DLT[Pred[x.sub.1]] for the first sample in the current block. The
encoding apparatus maps the DLT to an original depth value
Org[x.sub.1] of the first sample in the current block, which is
derived based on the intra prediction mode of the current block to
derive a second index value DLT[Org[x.sub.1]] for the first sample
in the current block. In addition, the encoding apparatus may
derive a residual index value Res_index[x.sub.1] between the first
index value DLT[Pred[x.sub.1]] and the second index value
DLT[Org[x.sub.1]] for the first sample in the current block. The
derived residual index value Res_index[x.sub.1] is used as the
residual signal for the first sample in the current block to
perform the transformation, quantization, and the entropy encoding
of the current block.
[0129] The encoding apparatus may transforms, quantizes, and
entropy-encodes the residual index value for each sample in the
current block (S530).
[0130] The residual signal of the current block is generated by
using the DLT as described above to reduce the number of bits to be
encoded and the DLT is applied even to the existing intra
prediction mode in addition to the SDC mode to increase encoding
efficiency.
[0131] According to the embodiment of the present invention, in the
encoding method using the DLT, the encoding may be performed by
using the DLT only when the current block has a size of 2N.times.2N
in order to reduce complexity. The intra prediction is performed
even in a block size of N.times.N in addition to the block size of
2N.times.2N. However, in most cases, since the intra prediction is
performed in the block size of 2N.times.2N, the aforementioned
steps S500 to S530 by applying the DLT when the current block has
the size of 2N.times.2N in order to reduce the complexity in the
present invention.
[0132] Further, in the present invention, in the encoding method
using the DLT, the encoding may be performed by using the DTL only
in the case of a specific intra prediction mode in order to reduce
the complexity. In general, since samples in the prediction sample
are generated by applying an interpolation filter in residual intra
prediction modes other than the DC mode, the horizontal mode, and
the vertical mode among the intra prediction modes, all values of
the samples in the prediction block are different from each other.
In this case, applying the DLT as an average value of all samples
in the block decreases the encoding efficiency. Accordingly, in the
present invention, instead of applying the DLT to all of the intra
prediction modes, the DLT is applied only to the DC mode, the
horizontal mode, the vertical mode, and the depth map intra
prediction mode that generate the prediction mode without applying
the interpolation filter to perform the aforementioned steps S500
to S530. In this case, the encoding apparatus need not encode
information (for example, a DLT flag) indicating whether the DLT is
applied and has a gain in which the complexity decreases.
[0133] Meanwhile, the encoding apparatus compares a residual signal
generated by using the value and a residual signal generated by
using the index in terms of rate distortion optimization (RDO) in
order to select an optimal intra prediction mode for the current
block. In this case, since the encoding apparatus performs the RDO
twice for each of all intra prediction modes, the complexity may
increase. Hereinafter, the present invention provides a method for
selecting the optimal intra prediction mode in order to reduce the
complexity in the encoding method using the DLT.
[0134] FIG. 6 is a flowchart schematically illustrating a method
for selecting an optimal intra prediction mode according to an
embodiment of the present invention.
[0135] The encoding apparatus may perform a process given below in
order to decide the intra prediction mode a block (current block)
in which the prediction is currently performed.
[0136] Referring to FIG. 6, the encoding apparatus generates 8
candidate intra prediction modes having low cost among 35 existing
intra prediction modes through simplified RDO and selects 4
candidate intra prediction modes having low cost among 8 candidate
intra prediction modes again (S600). In this case, a candidate list
may be generated based on 4 candidate intra prediction modes.
[0137] Herein, 4 candidate intra prediction modes are finally
selected among 35 existing intra prediction modes, but this is just
one example and the number of candidate modes may be variably
controlled.
[0138] The encoding apparatus adds the depth map intra prediction
modes (for example, the DMM, the DC mode, and the planar mode) to
the candidate list constituted by 4 candidate intra prediction
modes (S610). In this case, how many modes among the depth map
intra prediction modes are to be added may be variably
controlled.
[0139] The encoding apparatus performs final RDO (full RDO) with
respect to the candidate list constituted by 4 candidate intra
prediction modes and the depth map intra prediction modes
(S620).
[0140] The encoding apparatus compares cost of 4 candidate intra
prediction modes and cost of the depth map intra prediction modes
(for example, the DMM, the DC mode, and the planar mode) which are
acquired through the final RDO (S630) and selects the optimal intra
prediction mode having low cost (S640).
[0141] The encoding apparatus may decide the selected optimal intra
prediction mode as the intra prediction mode used for
intra-predicting the current block and signal information on the
intra prediction mode of the current block to the decoding
apparatus.
[0142] When the depth map intra prediction mode is selected as the
optimal intra prediction mode, the encoding apparatus may signal
information indicating that the intra prediction is performed by
using the depth map intra prediction mode to the decoding
apparatus. On the contrary, when the existing intra prediction mode
is selected as the optimal intra prediction mode, the encoding
apparatus may signal information indicating that the depth map
intra prediction mode is not used to the decoding apparatus. That
is, the encoding apparatus may signal flag information indicating
whether to use the depth map intra prediction mode.
[0143] Further, the encoding apparatus may decide whether to
perform the intra prediction encoding using the DLT through the
aforementioned steps S600 to S640 by considering rate distortion
cost and signal information indicating whether the DLT is used to
the decoding apparatus.
[0144] FIG. 7 is a flowchart schematically illustrating a method
for decoding by applying intra prediction using a DLT according to
an embodiment of the present invention. The method of FIG. 7 may be
performed by the video decoding apparatus of FIG. 3.
[0145] Referring to FIG. 7, the decoding apparatus acquires the
residual index value for a block (hereinafter, referred to as the
current block) to be currently decoded in the depth-map picture
through entropy decoding, dequantization, and inverse
transformation (S700).
[0146] The decoding apparatus performs the prediction based on the
intra prediction mode of the current block to derive the predicted
depth value of each sample of the current block. In addition, the
decoding apparatus maps the depth lookup table (DLT) to the derived
predicted depth value of each sample of the current block to derive
the index value of each DLT (S710).
[0147] Herein, the intra prediction mode may be any one of the
aforementioned existing intra prediction mode (35 intra prediction
modes used to predict the texture video) and the depth map intra
prediction mode (the SDC mode including the DMM).
[0148] Alternatively, the intra prediction mode may be a specific
intra prediction mode and for example, any one of the DC mode, the
horizontal mode, the vertical mode, and the depth map intra
prediction mode.
[0149] As described above, the DLT as the lookup table storing the
depth value of the depth-map picture has the information in which
each depth value is mapped to the index value.
[0150] For example, in the DLT, the depth value of the i-th index
may be derived based on the difference between the depth value of
the i-th index and the depth value of the (i-1)-th index in the
DLT. The decoding apparatus may derive the depth values in the DLT
based on the difference value between the indexes signaled from the
encoding apparatus.
[0151] The decoding apparatus adds the index of the depth value
predicted with respect to each sample of the current block and the
residual index to acquire the depth value of each sample in the
current block (S720).
[0152] For example, the decoding apparatus may acquire the residual
index value Res_index[x] for the current block through the entropy
decoding, the dequantization, and the inverse transformation. The
decoding apparatus may derive the predicted depth value
Pred[x.sub.1] of the first sample of the current block based on the
intra prediction mode of the current block. In addition, the
decoding apparatus maps the DLT to the predicted depth value
Pred[x.sub.1] of the current block to derive the first index value
DLT[Pred[x.sub.1]] for the first sample in the current block. The
decoding apparatus adds the first index value DLT[Pred[x.sub.1]]
for the first sample of the current block and the residual index
value Res_index[x.sub.1] to reconstruct the depth value of the
first sample in the current block. In this case, the depth value of
the first sample in the current block is a value acquired by
mapping the second index value
DLT[Pred[x.sub.1]]+Res_index[x.sub.1] derived by adding the first
index value and the residual index value to the DLT and
transforming the mapped second index value into the depth
value.
[0153] As described above, in the present invention, in order to
reduce the complexity, the aforementioned steps S700 to S720 may be
performed when the current block has the size of 2N.times.2N.
[0154] In the aforementioned illustrated system, methods have been
described based on flowcharts as a series of steps or blocks, but
the methods are not limited to the order of the steps of the
present invention and any step may occur in a step or an order
different from or simultaneously as the aforementioned step or
order. The aforementioned embodiments include examples of various
aspects. Therefore, all other substitutions, modifications, and
changes of the present invention that belong to the appended claims
can be made.
* * * * *